中文摘要：

结合实测数据，以三个对数正态分布函数的和函数为拟合函数，以梯度下降法为主要方法，对沉积物粒度分布进行了数据拟合，通过数值实验我们发现：利用梯度下降法可以有效地优化分布函数的各参数，实现拟合残差的稳步持续减小，具有良好的可操作性，拟合效果是令人满意的，它为我们进行数据拟合提供了一条新的思路，同时此方法也可以推广到解决其他极值问题．

英文摘要：

The gradient descent （GD） method is used to fit the measured data （i.e. the laser grain-size distribution of the sediments） with a sum of three weighted lognormal functions. The numerical results indicate that the GD method not only operates easily but also could effectively optimize the parameters of the fitting function with the error decreasing steadily. Meanwhile the overall fitting results are satisfactory. As a new way eft data fitting, the GD method could also expand to be used to solve other optimization problems.